Fetal and Childhood Growth and Development
Core concepts
Master the vocabulary of growth: small for gestational age (SGA) vs intrauterine growth restriction (IUGR) vs constitutionally small; symmetric vs asymmetric growth restriction. Symmetric restriction reflects early (often chromosomal or infectious) insults with proportional reduction in head and body, while asymmetric restriction reflects late placental insufficiency with head sparing. Know the distinction between proportional and disproportional growth and how each maps to timing and cause.
Understand normal growth curves, catch-up growth, and the difference between chronologic and corrected age in preterm infants. Recognize that somatic growth and neurodevelopment can dissociate. Be able to interpret bone age and pubertal staging as markers of endocrine vs nutritional vs constitutional delay.
Traps
Examiners love to conflate SGA (a statistical descriptor) with IUGR (a pathologic process)-an infant can be SGA without being growth-restricted and vice versa. Another trap: assuming all symmetric restriction is genetic; congenital infections (e.g., CMV) also produce symmetric patterns. Watch for questions that hinge on head circumference sparing as a marker of placental insufficiency versus microcephaly as a marker of early CNS insult.
Worked example / rule of thumb
A term infant at the 3rd percentile with normal length/head but low weight and a small placenta suggests late asymmetric restriction from placental insufficiency. Rule of thumb: "Head spared → late/placental; head involved → early/systemic." Plot on the correct curve before interpreting.